override pitch maneuver


I have a question related to the simulation of load cases like IEC ed3 DLC2.4 (NTM with grid loss). I run FAST with a control dll but it does not contain the safety functions only the normal operating pitch and torque scheme. I trigger the grid loss using the TimGenOf parameter and then overide the pitch with a ramp with the last parameters of the control block in fst-file. Unfortunately here, I can only input the time/position to start overriding and the time/position to stop. The problem is that I usually don´t know upfront the position of the pitch at the time of grid loss due to turbulence and various seeds and I want to pitch out with a fixed rate.

Is there any work around to that? Or is there any possibility outside simulink/dll to just have the ramp only defined by pitch speed and final value (like 90°).

Thank you for your support!


Dear Florian,

Your approach to modeling DLC 2.4 sounds correct. I understand the problem you are facing – you want to specify the time to initiate the pitch override, the pitch rate, and the final pitch, but you must give the end time instead of the pitch rate.

To get around this, I’ve made a small customization to FAST that allows me to specify the pitch rate instead of the end time. We plan to include this change in the next release of FAST. (Likewise for the override yaw maneuevers.)

Until this release becomes available, you have 3 options:

  1. Accept the fact that you don’t have the exact pitch rate that you want during the shut down.
  2. Implement the customization mentioned above yourself.
  3. Run the load case simulation twice. The first simulation can be used to determine the pitch angle at the time the pitch override is initiated. This value can be used to calculate the end time based on the desired pitch rate. Rerun the simulation with this end time.

Best regards,

OK thank you for the quick reply!